3,5-Lutidine coordinated zinc(II) aryl carboxylate complexes: Precursors for zinc(II) oxide

Abstract

The reaction of Zn( κ 2O,O′–OAc) 2·2H 2O with two equiv of 3,5-lutidine in methanol at room temperature for 12 h afforded [Zn(OAc) 2(3,5-lutidine) 2]· H 2O ( 1) in 91% yield. The acetate exchange reaction of 1 with two equiv of aryl carboxylic acids in methanol at room temperature for 12 h afforded [Zn( μ 2- κ 1O: κ 1O′–O 2CAr) 2(3,5-lutidine)] 2 [Ar = C 6H 5 ( 2) and C 6H 4Me-3 ( 3)], [Zn(OC(O)C 6H 4Me-2) 2(3,5-lutidine) 2] ( 4) and [Zn( κ 2O,O′−O 2CC 6H 4Me-4) 2(3,5-lutidine) 2] ( 5) in ⩾90% yield. Complexes 1– 5 were characterized by microanalytical, IR, solution ( 1H and 13C) and solid-state cross-polarization magic angle spinning 13C NMR and X-ray diffraction data. The zinc atom in 1 is surrounded by nitrogen atom of two 3,5-lutidine and oxygen atom of two monodentate acetate moiety and thus attains a tetrahedral geometry. One of the acetate moieties is hydrogen bonded with a water molecule in the crystal lattice. Complexes 2 and 3 possess a dinuclear paddlewheel framework with a square pyramidal geometry around the zinc atom whereas 4 and 5 are mononuclear species with the zinc atom in tetrahedral and an octahedral geometry, respectively. Thermogravimetric analyses of 2– 5 suggested ZnO as the decomposed product followed by the confirmation from the powder X-ray diffraction patterns. Enormous gas evolution resulting in porous ZnO during thermal decomposition was evidenced from scanning electron microscopic images.